The present invention relates to optoelectronic sensors, and especially to code readers, and to a method for operating such sensors, which involves receiving reflected light of a complete picture or visual representation line-by-line with a light receptor and compressing at least some of the pictures with a picture compression algorithm.
Optoelectronic sensors such as code readers read codes, such as one-dimensional bar codes or two-dimensional matrix codes, and they operate according to a variety of principles. Code readers which employ the scanner principle read the code by scanning a light beam over the object in question, for example a label carrying a bar code. Light reflected or returned by the object is received by a light receptor and converted into electronic signals. Bar code information is derived from amplitude information of the electronic signals.
Two-dimensional codes are typically read with code readers that operate on the camera principle. The object in question is illuminated with surface lighting or line-like light fields, which results in light that is reflected or returned by the object and received by a one- or two-dimensional receiver array, for example a CCD or CMOS line or matrix sensor. By making use of the amplitude differences of the received pixels, the code and therefrom code information can be derived.
U.S. Pat. No. 5,703,349 discloses a portable code reader which compresses received pictures prior to further processing them to facilitate, for example, their wireless transmission.
The compression of pictures is also useful for a variety of other applications. Such applications include, for example, the storage of selected pictures, such as reference pictures or pictures containing errors, which can be used for the subsequent analysis of errors, or test pictures with which the sensor can learn certain parameters, and similar uses.